1. Field of the Invention
This invention relates to a dust collector for radioactive particles and other dust particles in general.
2. Description of the Prior Art
Facilities handling radioactive materials are often provided with equipment for handling powder particles having radioactive materials mixed therein, where negative pressure control is performed by employing a suction system using a blower or the like to maintain a negative pressure in the system inside the equipment. With such negative pressure control performed, it is a matter of course that powder particles containing radioactive materials are carried by the air current. In the case where a thermal means such as melting or sintering is employed for volume reduction and compaction of noncombustible powder particles such as incineration ashes containing radioactive materials, there collect in large quantites in the off-gas system the incineration ashes themselves or gases and a thermal decomposition product called a fume, so that it becomes necessary to remove these substances.
Generally, under said negative pressure control, for cleaning the exhaust air current and removing these powder particles, use is made of a high efficiency performance filter called the HEPA filter. The HEPA filter, though high in performamce, is liable to be clogged with collected powder particles and is used primarily on a throwaway basis. Thus, an economical arrangement would be to dispose a filter of large collection capacity at the stage preceding the HEPA filter. It would be thought to use a bag filter as this pre-stage filter, but generally a bag filter has a small filtration area, so that a large bag filter must be used. This increases the danger of radioactive powder particles flying away and makes exchange operation difficult.
Further, in collecting general air-borne dust, if the amount of dust is large it is desirable to continuously discharge collected dust separately from the step of removal of the filter. In that case, it is desirable that exchange of filters be made in a sealed space.